I like your custom build of Luma. If you don't mind a suggestion, you should try to remove the autocopy of the boot.firm to the nand. Don't know why they thought that was a good idea.
Eventhough the New 3DS XL is more powerful, I still feel like the DS Lite was a more polished system. It's a real shame that it never got an XL variant keeping the GBA slot. You'd have to go on AliExpress and buy an ML shell to give a DS phat the unofficial "DS Lite" treatment, and that's the best we'll ever get I'm afraid.
@Jayro, I don't see whats so special about the DS ML, its just a DS lite in a phat shell. At least the phat model had louder speakers, whereas the lite has a much better screen.